20621579503661 has 4 divisors (see below), whose sum is σ = 20621664313824. Its totient is φ = 20621494693500.

The previous prime is 20621579503561. The next prime is 20621579503663. The reversal of 20621579503661 is 16630597512602.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20621579503661 is a prime.

It is a super-2 number, since 2×20621579503661² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20621579503663) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 42039305 + ... + 42527006.

It is an arithmetic number, because the mean of its divisors is an integer number (5155416078456).

Almost surely, 2^{20621579503661} is an apocalyptic number.

It is an amenable number.

20621579503661 is a deficient number, since it is larger than the sum of its proper divisors (84810163).

20621579503661 is an equidigital number, since it uses as much as digits as its factorization.

20621579503661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 84810162.

The product of its (nonzero) digits is 4082400, while the sum is 53.

The spelling of 20621579503661 in words is "twenty trillion, six hundred twenty-one billion, five hundred seventy-nine million, five hundred three thousand, six hundred sixty-one".